Today | Weather | Wednesday, May 20, 2026

Weather in Castle Rock, Colorado

03:53 PM
Now
Stormy Weather
54° F
Feels Like 48°
Precipitation 67 %
Wind 8 mph
UV Index (0 - 11+) 1
Humidity 70 %
Today
Sunny with a Chance of Thunderstorms
Day 55°
Night 37°
Precipitation 92 %
Wind 8 mph
UV Index (0 - 11+) 10

Warning: High UV Index Today: 10

High risk of harm from unprotected sun exposure. Take precautions: wear a hat, sunglasses, and apply sunscreen regularly if you’ll be outdoors for extended periods.

Castle Rock Weather Forecast Updated

Last updated on
Weather Forecast History
Last Year's Weather on This Day (May 20, 2025)

Day

70°

Night

37°

Air Quality in Castle Rock

NOW
40 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 1.02 µg/m³
PM10 2.24 µg/m³
O3 0.044 ppm
NO2 0.1 ppb
SO2 0.1 ppb
CO 0.08 ppm
NH3 0.82 µg/m³
NO 0.03 µg/m³
PM2.5 – Fine particles <2.5μm
PM10 – Inhalable particles <10μm
O3 – Ozone
NO2 – Nitrogen dioxide
SO2 – Sulfur dioxide
CO – Carbon monoxide
NH3 – Ammonia
NO – Nitric oxide

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

Show raw pollutant concentrations (µg/m³)
PM2.51.02 µg/m³
PM102.24 µg/m³
O385.81 µg/m³
NO20.17 µg/m³
SO20.16 µg/m³
CO89.91 µg/m³
NH30.82 µg/m³
NO0.03 µg/m³